The present invention relates to the field of surface coatings that are useful for reduction of protein adsorption and/or cell adhesion and for presentation of binding ligands.
Numerous methods can be used to coat surfaces. Hydrophobic interaction between block copolymers may be used to coat hydrophobic surfaces for subsequent use in aqueous environments. Examples of copolymers include block copolymers of polyethylene glycol blocks as a hydrophile and polypropylene glycol blocks as a hydrophobe. These materials adsorb upon the hydrophobic surface, with the strength of the interaction depending, for example, upon the hydrophobicity of the substrate, the hydrophobicity of the adsorbing block, the method of preparation of the interface, or the existence of any specific interactions between the adsorbing block and the hydrophobic substrate. The strength of the interaction is often not as strong as desired.
Chemisorption of thiols, disulfides, and derivatives thereof can be used to induce stable adsorption on metal surfaces, such as gold, silver, and copper. Thiols, alkane thiols, disulfides, and derivatives thereof, typically form a coating of close-packed independent chains when chemisorbed to a surface. Applications of thiol or disulfide surface coatings include, for example, corrosion prevention, adhesion promoters for organic coatings, lubrication, presentation of different chemical functional groups to an interface, surface patterning, and alteration of surface energetics. Common thiols, alkane thiols, and disulfides include octadecanethiol, hexadecanethiol, ω-oligo(ethyleneglycol) alkane thiols, and dimethyl disulfide. These materials are typically applied to surfaces, such as gold, silver, or copper from solution, e.g., ethanol or hexane.
When chemisorbed as a surface coating, the spacing of pendant chains, extending from the thiol or the disulfide sulfur atom(s), is typically dictated by the interaction of sulfur with the surface, e.g., gold, silver, or copper. This dictated spacing is a significant drawback in some applications, as the resistance afforded to protein adsorption may not be sufficient. The surface coverage of pendant chains also may be difficult to control. Additionally, alkane thiols are not very kinetically inert, i.e., replacement by other interactive molecules is likely to occur at defects of the coating upon long-term exposure to such molecules.
In view of the foregoing, there is a need for new types of coatings that bind strongly to a surface, are kinetically inert, and provide flexibility in the density of pendant groups.